Effect of the pretreatment of recast Nafion membranes on their rejection of the albumin interference in anodic stripping voltammetry

The title subject was examined using cadmium and lead as test analytes and differential pulse anodic stripping voltammetry as detection method. Ultrat hin (ca. 0.3 mum) Nafion coatings were deposited on glassy carbon by electr ostatic spray deposition. This technique proved far superior to evaporative casting with respect to the uniformity of the polymer layer. Overall, it w as found that the pretreatment of the Nafion coating had a major effect on the extent of the albumin interference. Swelling of the Nafion coating in n itric acid and lithium hydroxide significantly reduced albumin interference , whereas treatment with sodium hydroxide and cesium hydroxide did not have an effect. Heat treatment (140 degreesC) of Nafion in the H+ form worsened the albumin interference, and the same trend was seen for the Na+ and Csforms but not for the Li+ form. These results show that the degree of album in interference is determined not only by the permeability of the coating b ut also by adsorption onto the outer surface of the membrane. The experimen tal results are explained in terms of the conformational changes of Nafion induced by the pretreatments.